Shannon McCauley: The Rise of Community Ecology

Community ecology is one of the more recent ecological disciplines, and has enjoyed a rise in popularity in the last decade. Yet it’s often been criticised as a little obscure, and has had difficulties integrating with other branches of ecology like evolution and population dynamics.

With this in mind, I sat down with Doctor Shannon McCauley of the University of Toronto during her recent visit to the University of Arkansas. Shannon is a community ecologist at the University of Toronto-Mississauga who uses dragonflies and other aquatic insects to answer questions about dispersal, community connectivity, and the effects of climate change. We attempted to put a little more context behind community ecology, and highlighted its relevance in the coming years.

Adam Hasik (AH): Community ecology is a relatively new discipline. One of the issues that we seem to have had is integrating community ecology with other disciplines like evolutionary biology. How should community ecologists tackle this problem?

Shannon McCauley, Assistant Professor of Biology, University of Toronto (SM): The fact that there are so many things that can fit under this box of community ecology has sometimes led people to be slightly dismissive of it. People think we just study whatever we want. But really, it’s a study of ecology that involves multiple species and their interactions, with both each other and with the landscape in which they’re situated. That gives us a better perception.

There has been huge growth in meta-community ecology. It rose to address this idea of Macarthur’s Paradox, that we either look at local levels, very fine scale processes, or really big regional scale patterns. And then nothing in between. So meta-community ecology really grew to integrate processes at local levels and at regional levels. To answer questions like who is a member of this community, how diverse is this community, and what are the exchanges that occur between communities.

I would say that one of our weaknesses is understanding connectivity and how exchanges occur between communities. And this has huge implications for all sorts of aspects of ecology and evolution. I see dispersal as a really important linkage point between community ecology and evolution and even ecosystem ecology. It affects gene flow, it affects demographic connectivity or community connectivity. It’s also shaping exchange of nutrients and energy between systems. That’s one area where I think there’s tremendous potential to create a more integrated framework for eco-evolutionary studies.

AH: Community research can really help us shed light on how effects in one region can have significant demographic effects in another.

SM: Yes. There’s nice work being done on carry-over effects and things like how early stressors can have effects on later life events. Look at dragonflies for instance. At different life stages they have different forms, but it’s the same animal. You have this aquatic stage, it breathes through gills, but its still the same animal that has to fly between sites. They are fundamentally the same thing. So everything that happens in early life affects its ability, its propensity to move and live in those different sites, and what its offspring potentially do.

There are really neat epigenetic patterns happening here. But there’s also simpler questions like how big are you, how much did you grow? How will your growth in one region affect your activities in another if you disperse? How big you are determines how many resources you need in that new environment.

AH: Climate change is a huge issue these days, but fragmentation, which is also incredibly important, has faded a little in the public consciousness. Why do you think fragmentation isn’t talked about as much?

SM: People think it’s an issue that’s been addressed, which is bizarre. There was a time when fragmentation was much more of a topic in conservation biology than climate change. I think people got this idea that we’ve “figured out” fragmentation. Which we certainly have not. And also I don’t think people are thinking about the connection between fragmentation and climate change. A major response to climate change is that species move and follow those cooler conditions polewards. That’s not happening in an intact environment, that’s happening in a fragmented environment. And so we need to look at landscape context, how will that affect the capacity of these organisms to shift? It’s absolutely a critical topic.

I think there’s also a bit of an issue in North America with reforestation. Throughout a lot of New England and the upper Midwest, it’s more forested now than it was at the turn of the century, early 1900s. There’s work that’s been done in New England that shows we’re at the highest forest levels in 200 years. BUT, that’s because 200 years ago it was really deforested. Everyone’s perception is very much shaped by what we experience as kids. So this is an environment that has a mix of field and forest, and now we see even more forest, things must be great! But our reference points are not ecological reference points, they’re personal.

You also need to consider the nature of barriers. Agriculture can be a better environment for pavement for an insect, if for instance it’s not heavily sprayed with pesticides. We sometimes perceive these environments as being much better than they actually are. So for us, something might look like habitat, there’s some trees at the edge, there’s a big field of soy beans, that’s not so bad, but for organisms it’s an ecological desert.

Human perceptions are not what’s important here. It’s the organisms perceptions. But we’re biased by what we see and what we experience.

AH: People also make some dangerous assumptions about habitat connectivity.

SM: Yes, the idea of something like movement capacity, this is something we’ve faced a lot with dragonflies, people say “they fly, so they can get anywhere”. And yes, they might have the capacity to do it, but they might just have a very strong behavioural propensity not to. Many species are much more likely to stay in the environment they were born in than you’d expect. They may come out of a pond and never go more than a few hundred metres from it.

I think our perception of capacity to move equalling this behavioural propensity to do so is flawed, and so often at times we don’t worry about a population because we think it can shift, so it will. Birds are great example. In the tropics, there are specialist birds who simply won’t cross pastures. They could easily fly that distance, but they won’t cross into that environment. You haven’t put up a brick wall, but you might as well have. You need to have that organismal perspective. It’s not what you would move through, it’s what they would.

People tend to assume that because an organism can fly, like this Blue Dasher dragonfly, it can move from “bad” habitats, but the reality it much more complicated than that, and most organisms don’t move far from where they are born. (Image credit: Adam Hasik)

AH: Conservation of entire patches is obviously very important then. But it’s hard to get the public to care about an ecosystem, and much easier to get them to care about a single species. Is there a way to merge the two? And should we?

SM: I think that’s a really difficult issue. There is an emotional attachment, and conservation has this emotional component. You can see why, pandas are adorable, and polar bears are really cool! I think they can go hand in hand when we have umbrella species. Often you’ll have a top predator or something that requires a lot of space, which is very charismatic. So if we conserve what’s required for this species, and you can protect the area for it, all sorts of other species and all sorts of other ecosystem properties and processes are then protected under that umbrella and can flourish. But if you’re managing that habitat for a single species, are you managing it the best way? Also, and unfortunately I think we’re facing this reality, if that species goes extinct, does that mean that habitat loses all value?

It’s something that can absolutely be a very successful strategy, and I think it is an important one! If you’re targeting the right species, you’re often protecting that whole ecosystem. You get that emotional hook, and you also create an important platform for scientists and conservationists to communicate. So that the value of that ecosystem is recognized. So that this is not simply about one species, but it’s about intact systems.

AH: So how do we get people to care about ecosystem processes?

SM: The things is, people take care of what they love. It’s harder to love carbon cycling than wolves, for instance. I get that, I know carbon cycling is really important, but I don’t get excited when I see it. Wolves, that’s exciting. But one of the things you can do with science education is bring in both of those things and say “look at this amazing organism, and here are all the things it’s effecting”. And you make people more aware of the complexity of these systems.

Take an aquatic ecosystem. There’s all this hidden biodiversity. We don’t see under the water well, and there are these amazing fish species and amazing invertebrates down there. But often, people have no awareness of that. And they do care about it, once they know. So we need to bring to light some of these species that otherwise are very easy to overlook. I always love caddisflies. These wonderful little insects that make homes out of stones or leaves and sew them together on themselves in their larval stage in the water. And when you actually show someone that, that becomes charismatic.

I often refer to odonates (damselflies and dragonflies) as charismatic mesofauna. People do like them. They’re not polar bears, but they are interesting and exciting. People can go looking for odonates now when they used to go birding, and it has really increased interest. When you really stop and look at nature, it’s beautiful. But maybe you just never stop to look at the right parts.